The invention relates to soil surface cultivating machine of the kind comprising a tined rotor.
Soil surface cultivators have been provided for many years and have the requirement that there should be a shallow tillage of the surface of the ground and this should ideally be carried out at a relatively high speed of movement over the ground.
The problem which has consistently arisen with rotary cultivators of the power-driven kind is that in order to obtain a high rate of work at a shallow depth a very large amount of power is required.
It has generally in the past been assumed that when the surface cultivator comprises a rotary device rather than a reciprocating device the rotor must run in the same direction as the wheels of a tractor pulling the device and at a higher peripheral speed than the forward speed of the implement, and since power absorption is in part a function of the speed of the rotor tines through the soil a high power requirement results.
Similarly in those embodiments where the rotor is arranged to run in the opposite direction to that of the wheels of the pulling vehicle the speed of the tines through the soil is the sum of their peripheral speed and the forward speed of the implement, and the power requirement is correspondingly high.
Thus, single rotor cultivators have generally had a high power requirement.
Proposals have also been made for other forms of soil working devices, such as pulverizers and root grubbers in which one rotor or rotary device is used to drive another rather than using the power take-off of a tractor to which the device is attached. U.S. Pat. No. 2,722,876 (London), for example, describes a soil pulverizer in which two pronged rotors are interconnected by a chain such that there is a slight rotational speed difference between the rotors. This device, is, however, wholly unsuitable for soil surface cultivation of the kind with which this invention is concerned because thr prongs of the London device will not till the soil.
A root grubber is described in U.S. Pat. No. 2,771,828 (Troeng et al) in which a wheel frictionally engages the ground in order to drive a raking wheel eccentrically so that the raking claws have a relatively low speed while scratching the roots away and the raking wheel has a relatively higher speed as it passes from one claw to the next. Again, this machine is unsuitable as a soil surface cultivator because the claws of the raking wheel scratch the ground rather than engaging and lifting the soil and the friction wheel does not engage the soil in order to lift the soil.